Comparison of plasma levobupivacaine concentrations with and without epinephrine following erector spinae plane block for breast cancer surgery: a randomized controlled trial

BACKGROUND: The erector spinae plane (ESP) block requires a large volume of local anesthetic to provide effective analgesia, which has the potential to cause local anesthetic systemic toxicity (LAST). Adjunctive epinephrine slows the entry of local anesthetic into the plasma and decreases its toxic effect on vulnerable tissues. We compared plasma levobupivacaine concentrations with and without epinephrine after ESP blocks for breast cancer surgery. METHODS: In this prospective, double-blinded, randomized controlled trial, 35 patients who underwent elective unilateral partial mastectomy with sentinel lymph node biopsy were enrolled. The patients were randomized to group L (ESP block with 2 mg/kg levobupivacaine) or LE (ESP block with 2 mg/kg levobupivacaine and 5 μg/mL epinephrine). Blood samples were obtained at 2.5, 5, 7.5, 10, 12.5, 15, 30, 60, and 120 min after the ESP block, and plasma concentrations of levobupivacaine were compared. RESULTS: Twenty-nine patients were included in the analysis. The maximum plasma concentration (C(max)) and the time to maximum concentration (T(max)) were, respectively, 1.24 μg/mL and 6.0 min in group L and 0.62 μg/mL and 7.2 min in group LE. The two groups showed no significant differences in the numerical rating scale scores immediately after extubation and 5 and 9 h after the ESP block, or in the interval from the ESP block to the first rescue analgesia. No patient developed symptoms suggestive of LAST. CONCLUSIONS: A single bolus of 2 mg/kg levobupivacaine in the ESP block resulted in a short T(max) with high C(max). Adding epinephrine to levobupivacaine decreased the C(max) and delayed the T(max) after ESP blocks but had no effect on postoperative analgesia. TRIAL REGISTRATION: UMIN Clinical Trials Registry, UMIN000034479. The trial was retrospectively registered on October 13, 2018. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-022-01632-6.